Effect of Cd on growth, photosynthetic gas exchange, and chlorophyll fluorescence of wild and Cd-sensitive mutant rice

Growth, photosynthetic gas exchange, and chlorophyll fluorescence characteristics were investigated in wild type (WT) and Cd-sensitive mutant rice (Oryza sativa L.) plants using 50 mu M Cd treatment for 12 d followed by a 3-d recovery. Under Cd stress, net dry mass and pigment contents were significantly lower in the mutant plants than in the WT. The mutant had lower net photosynthetic rate (P-N), transpiration rate (E), and stomatal conductance (g(s)) than WT rice, however, it had higher intercellular CO2 concentration (C-i), indicating that non-stomatal factors accounted for the inhibition of P-N. Maximal photochemical efficiency of photosystem 2 (F-v/F-m), effective quantum yield of PS2 (Phi(PS2)), and photochemical quenching (q(P)) decreased much in the mutant under Cd stress. Cd content in roots and leaves of the mutant was significantly higher than those in the WT. Hence Cd toxicity was associated with the marked increases in Cd contents of plant tissue. After the recovery for 3 d, the WT rice had higher capacity to recover from Cd injury than the mutant.